Inkjet printers provide an inexpensive means for printing documents from a personal computer. A conventional inkjet printer includes a movable inkjet printhead mounted on a carriage assembly. The carriage assembly moves the inkjet printhead over a print medium, such as paper. The printhead has an ink supply and an array of nozzles which generate ink droplets as the printhead moves over the paper to produce a desired image on the paper. Each nozzle is formed by a nozzle chamber, a firing mechanism, and an orifice, with the firing mechanism being located within the nozzle chamber. During operation, the nozzle chamber receives ink from the ink supply and the firing mechanism is activated, thereby causing an ink droplet to be fired from the chamber through the orifice onto the paper. A roller moves the paper in a direction perpendicular to the motion of the printer head so that the printhead nozzles can progressively lay down segments of the desired pattern.
A trend in inkjet printer technology has been to increase the number and the density of inkjet nozzles, which can result in increased resolution of images produced by the printhead. The increased number of nozzles can also decrease the distance which the printhead is required to travel, if additional nozzles are added laterally in the direction of travel of the printhead. The printhead has less distance to travel, because the nozzles of the printhead are located closer to the opposed margins of the paper as the printhead begins to traverse the paper. U.S. Pat. No. 5,742,305, which is assigned to the assignee of the present invention, describes a page-wide-array (PWA) printer element which has an array of inkjet nozzles spanning the width of a paper. While a conventional inkjet printer head has approximately 100 to 200 inkjet nozzles, the PWA printer element has between 5,000 and 7,000 inkjet nozzles. Consequently, the PWA printer element is able to remain stationary while it prints an entire line across a page.
Although the PWA inkjet printer is able to increase print speed significantly by printing an entire line at once or multiple lines simultaneously, the complexity introduced by the increased number of inkjet nozzles is significant. For an eleven-inch (279.4 mm) printhead with 600 dots per inch (23.62 dots per millimeter), there are at least 6600 nozzles.
What is needed is an inkjet printer which provides increased print speed over conventional scanning printhead inkjet printers and which enables simultaneously printing in multiple print modes.